1. Field of the Invention
The present invention generally relates to a fuze having an interrupted energy transfer mechanism and, more particularly, is concerned with a safe and arm device that incorporates a fire-on-the-fly bi-stable barrier component that does not stop in an armed position with parts of the energy transfer mechanism in alignment.
2. Description of the Prior Art
Fuzes are physical systems designed to sense a target or the result of other prescribed conditions such as time, barometric pressure, command, etc., and initiate a train of fire or detonation in an item of ammunition (warhead, projectile, bomb with an explosive charge, pyrotechnic, chemical or other load). Safing and arming are functions performed by a device in the fuze to preclude initiation of the ammunition before the desired position or time.
The primary purpose of the safe and arm device is to prevent an unintended functioning of a main charge explosive of the ammunition, but allowing an explosive train of the ammunition to function after arming. An explosive train is one form of an energy transfer mechanism. It begins with a primary explosive that initiates detonation, continues through a booster explosive that transmits and augments the detonation reaction and terminates in the main charge explosive that achieves the end destructive result of the ammunition.
In an interrupted-type explosive train, the primary explosive detonation is physically separated from the booster explosive by an interrupter or barrier component of the safe and arm device. The barrier component, typically a slider or rotor, interrupts the explosive path and thus prevents detonation of the booster and main charge explosive until arming occurs. Arming occurs by moving the explosive train barrier component to align the explosive elements in the explosive train of the fuze.
Military standards establish specific safety requirements applicable to safing and arming functions performed by such devices of fuzes intended for use with munitions. One of the safety requirements is that the barrier component of the safe and arm device interrupting the explosive train must be directly locked mechanically in the safe position by at least two independent safety features which cannot be removed until arming begins.
Another safety requirement is that if the fuze should misfire or malfunction, the design must preclude the possibility of the safe and arm device producing a potentially hazardous dud. A hazardous dud would be produced if the barrier component of the safe and arm device remaimed in the armed position with the elements of the explosive train in alignment.
Still another safety requirement is that the fuze should not utilize stored energy to provide the energy for arming unless adequate environmentally-derived energy is unavailable. A component contains stored energy if the component itself is capable of delivering energy in addition to the external energy required to initiate its function. Examples of components containing stored energy are compressed gases, explosive actuators and loaded springs.